Plagiarism Checker
Check text for plagiarism by comparing it against up to 5 source documents. Uses Rabin-Karp fingerprinting to highlight matching phrases and show a similarity percentage. Free, private, runs entirely in your browser.
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— Help others discover itFrequently Asked Questions
How does the plagiarism checker work?
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It uses Rabin-Karp fingerprinting — a rolling-hash algorithm that breaks text into overlapping 5-word phrases and checks for exact phrase matches between your text and the source documents. Everything runs locally in your browser; your text is never sent to any server.
What does the similarity percentage mean?
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It shows what fraction of your text contains phrases also found in the provided sources. A 0% score means no matching phrases were found. A high score doesn't automatically mean plagiarism — it may reflect common phrases or intentional quotations.
How many sources can I add?
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You can add up to 5 source documents at once. Each source gets its own similarity score and colour-coded highlights.
Is my text sent to a server?
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No. All comparison runs entirely in your browser using JavaScript. Your input text and sources never leave your device.
Why are short phrases not flagged?
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The checker requires at least 5 consecutive matching words to flag a phrase. This avoids false positives from common short phrases like "in order to" or "as well as".